Many public safety or other private or government wireless communication systems provide for group-based radio communications amongst a plurality of radios (subscriber units). During the formation of a group, all radios within the group will share certain radio parameters (e.g., channel, alerts, . . . , etc). In certain situations, important alerts may need to be provided to the group or groups operating in a particular defined area. For example, at a mining site, events such as blasting operations impart unique alerting requirements on the wireless communication system and subscriber devices operating therein in preparation for, and perhaps during, a blasting operation. In other situations, a group or groups of subscriber devices may need to be alerted about events such as hazardous material leaks or weather alerts relative to a particular defined area. Other examples are possible as well.
Typical methods of signaling events such as blasting amongst subscriber units have historically relied upon an assignment of a separate RF channel over which predefined analog audio is mixed at the infrastructure and broadcast from the fixed terminal to the subscriber units, and played back at the subscriber units that are tuned to the separate RF channel, to indicate the respective event or hazard.
However, such typical methods provide a same alert (in this case, an alert tone) across a coverage area of an entire site or group, without an ability to selectively choose a particular alert based on the type of event or hazard, and/or to limit the alert to a particular area within a radio coverage cell of a base station broadcasting the alert. For example, a particular base station may provide wireless communications coverage over a 5 mile radius, but an alert may only be relevant to a one square mile area within the radio coverage cell. Furthermore, a relevant area may cross over two radio coverage cells of two adjacent base stations, in which case the alert may be broadcast over two large radio coverage cells when the alert is only relevant to a small sub-portion at the periphery of each radio coverage cell. Still further, common relevant areas may exist in multiple sub-portions of coverage areas, such as schools or parks. Other examples are possible as well.
In order to address the above, a geofence may be created that defines a particular area of interest. Those units within the geofence may have their radios operate in a similar manner (e.g., all tune to the same channel, all receive the same alerts, . . . , etc.) regardless of the infrastructure equipment being utilized.
Geofences may be mobile. For example, a caravan of users/vehicles may have a geofence created so that everyone within a predetermined distance from a particular vehicle operates in a similar manner. Consider a caravan guarding/carrying the President of the United States. All vehicles within the caravan may be within an established geofence that stretches miles.
A problem exists when geofences cross. When the geofence enables communication management between crossing geofences, this can have an adverse impact on the intra-communication activities of a caravan. Consider the situation where a vehicle, being part of a first geofence caravan, crosses over a second geofence. Should the vehicle change radio parameters? Doing so may effect the vehicle's ability to communicate with others in the caravan who haven't entered the second geofence. Accordingly, what is needed is an improved method and apparatus for changing geofence-based operating parameters for radios without hindering communications with other members of the geofence.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.